Dear Readers, those of us who have dipped our toes into the world of citizen science, by participating in the The Great Garden Birdwatch or Butterfly Conservation’s Butterfly Count often wonder what else we should be doing. There are national bird counts, to be sure, but can we sensibly do anything in our own back gardens? Dave Dawson has recorded the birds that he’s seen in his South London garden for the past thirty years, and he would reply with a resounding yes.
Dawson gave a number of reasons for recording the birds in your garden. Firstly there’s the delight of discovery, like the the time that he saw a raven flying over, being mobbed by crows. Then there’s the fact that quantitative information can be extremely useful, both at the time and for posterity. He posited the case of kangaroo numbers in Australia – there are many diary entries that say useful things like ‘we saw lots of kangaroos today but not as many as yesterday’. If only someone had thought to jot down some numbers! Then there’s the importance of documenting things as they actually change – Dawson could never have anticipated that there would be quite so many ring-necked parakeets in London, but neither could he have foreseen that house martin numbers would drop to zero.
Furthermore, counting birds is easily and conveniently done – Dawson remarks that he can do his count in the time that it takes him to brew up his Turkish coffee in the morning. Everyone now agrees that getting out into nature is good for you. And finally, Dawson’s method works – it will enable the user to actually record trends and to gather useful information.
Dawson agrees that to actually record a bird, you need three things – acuity, concentration and knowledge. However, all three can be accumulated by regular observation! He notes that, for himself, he wasn’t sure if the presence of cataracts and his gradual hearing loss impacted on his recording, though on balance I think he concluded that, although without his hearing aids in he ‘lost’ some species, like goldfinches, it didn’t impact on his figures overall. Because, as we’ll see, the recording sessions are so short it shouldn’t be difficult to concentrate. And knowledge of how the different species look and sound can be developed with the aid of field guides and mentors.
So, how does Dawson recommend going about observing and recording the birds in your garden?
Choose a point in your garden to use for observation. Anything within a 25 metre radius of this point counts as a ‘near’ bird, anything further than this (including birds flying over) count as ‘far’. (You can count birds that you see and those that you hear, if you are reasonably confident about bird song (Bug Woman))
Choose a routine that is easy and not too punishing. Most birds can be seen and heard between 8 and 10 a.m. so you won’t gain much by springing up at the crack of dawn.
Choose a point which is ‘sensible’ i.e. with a good view of the garden.
Choose a convenient counting frequency (i.e. a couple of times a week rather than every single day)
Avoid winds of more than Force 4 or heavy rain
Use a clipboard and a form – you will definitely want to record the date, time and how many birds of each species you saw, but Dawson also records temperature, wind speed, precipitation, cloud cover, and who actually did the count. Much depends on what you are personally interested in.
Count all species – don’t go missing out the feral pigeons, for example, because chances are you’ll suddenly want to find out something about them.
Count any birds that scatter on your arrival
Count for five minutes
Record the birds that you see within your 25 metres and the ‘far’ birds separately.
So, what sort of information can be produced, and why do this instead of (or as well as) some of the national recording schemes? Dawson found that his results for some species mapped very nicely onto the British Trust for Ornithology’s Breeding Bird survey, but for some his personal records were very different. Although there has been a precipitous decline in house sparrow numbers, for example, the species has disappeared from Dawson’s garden altogether, probably the result of his particular colony dying out. He has also recorded a dramatic fall in the number of blue tits, although they’ve stayed more or less stable in the country as a whole.
Dawson also mentioned another survey that was done in the London Borough of Sutton in 1989. There was a push locally for more high density housing, and Dawson was asked to survey the birds in low, medium and high density areas of the borough to see what the possible impact might be. The study was conducted in a similar way to Dawson’s garden survey, with different areas of similar sizes being compared for their species richness. The only species that favoured the close-packed terraced houses were house sparrows and starlings, but thirteen species were found much less often in such sites, and overall, twenty species were disadvantaged by high-density developments. So, bird counts can reveal a lot of information that can’t be extracted from anecdotal accounts alone. We need quantitative data to make sense of the world sometimes, and Dawson has an infectious love of statistics, honed over nearly sixty years of working in the field. I thoroughly enjoyed his talk, and if you want to watch the whole thing, you can find it here.
Dear Readers, while the subject of cetacean strandings is not a happy one, it is something that concerns many people. Are whales stranding themselves more frequently, and if so, why? Rob Deaville is the Project Manager for the Cetacean Strandings Investigation Team (CSI), and has been researching this subject for the past 21 years. He began by defining exactly what a stranding was: it’s
“when a live or dead marine mammal swims or floats onto shore and becomes ‘beached’ or incapable of returning to the sea”
Strandings can occur with individual or groups of whales, and they have been recorded throughout history. CSI looks at why strandings occur, and looks at whether the reasons are natural, or manmade.
Deaville started out with some historical context. Since 1324, when whales were described as ‘royal fish’, the monarch technically owns any stranded cetaceans that appear around the UK coast. In 1911 there was a mass stranding of over 50 pilot whales at Penzance in Cornwall, though the reaction of the local people was to chop the whales up, presumably for meat. However, it did alert the Natural History Museum (NHM) to the possibilities that strandings presented to learn more about cetaceans, which are very difficult to study in the wild. From 1913 onwards the NHM collected data on 3,949 strandings, and collected material for skeletal preparations from the dead animals (including one whale who was shipped across from Kings Cross on and open-bedded truck and dissected on the front lawn of the Museum). The modern stranding programme that Deaville is involved with started in 1990.
Deaville moved on to talk about 3 whale strandings in the London area. In 1658 a North Atlantic Right Whale stranded on the Thames and was dragged ashore and butchered by the local population for its oil. The skeleton of this whale, still showing the damage from the butcher’s knives, was found in Greenwich in 2010.
In 1954 ‘Jonah’ the whale was hunted off the coast of Iceland, embalmed and then taken round the country as a travelling freak show.
However, in 2006 a Northern Bottlenose Whale was seen in the Thames, as far upstream as the Houses of Parliament. Deaville was involved in the rescue attempt to try to return this whale to the open sea, although the animal unfortunately died in transit. As he says, we have gone from a nation of butchers and gawkers to a nation of conservationists – the response of the public to the rescue attempt was heartfelt and sympathetic.
Deaville then moved on to look at strandings more generally in the UK. He showed a chart that showed how strandings of fin whales and humpback whales had increased in the UK since the moratorium on whale-hunting in 1986, and how this is not necessarily a bad thing, as it can indicate that numbers of the whales are increasing, and hence we are starting to see them stranding (there were no humpback strandings in the UK prior to the ban on hunting).
Over the past 30 years there have been 17,000 strandings in the UK. 88% of these are where the cetaceans are already dead when they appear. By far the largest numbers of strandings are of smaller whales, with 8,615 harbour porpoises and 2915 common beaked dolphins comprising the bulk of the numbers, along with over 2,000 unidentified cetaceans who were presumably too decayed or damaged for the species to be ascertained. 7% of strandings are live animals, and the remainder are whales found entangled or floating at sea. In total, 22 species of whales have been identified from UK strandings, which is a quarter of all the whale species in the world, which reflects the diversity of our coastline, from the shallow coastal areas where harbour porpoises strand to the deeper, pelagic areas where sperm whales and humpbacks come to grief.
Deaville moved on to mass stranding events, which have occurred largely in Northern Scotland with one event in Cornwall. Organisations such as the RSPCA and local diving and rescue groups managed to rescue large numbers of the cetaceans involved (usually dolphins, porpoises or pilot whales) but many of the animals died. In two of the cases there seemed to be a direct link to human noise (probably use of sonar but Deaville didn’t go into detail on this).
Looking at the number of strandings, there seems to have been a marked increase during the period 2016-2019. There was also a reduction in strandings by cold-water species of cetacean, and an increase in strandings by warm-water species, which points to the impact of climate change.
Deaville then moves on to talk about the cause of death of the animals that he sees. A major reason for the demise of harbour porpoises and common dolphins is ‘by-catch’, whereby the animals get entangled in fishing nets. Harbour porpoises seem to be being killed all around the UK, but common dolphins are clearly most frequently killed around the south-west, particularly Cornwall. Deaville spoke of a ‘by-catch season’ for common dolphins from December to April, where they wash up dead but with evidence of damage from fishing nets.
Entanglement is a very specific form of by-catch that affects larger whales such as minke whales. Sometimes they drown because of a sudden entanglement in ship’s ropes, sometimes they die from starvation over a period of time when ropes and nets prevent them from hunting. Most of the cases are in Scotland where there’s a lot more creel-type fishing, using roped baskets to catch lobsters and crabs.
Ship strike, where animals are killed by propellors or being hit by a ship, largely affects harbour porpoises and common dolphins, and occurs, not surprisingly, where there are ports and a lot of shipping activity.
Not all causes of death are man-made, however. A significant cause of death is attack by bottle-nosed dolphins on other cetaceans, particularly harbour porpoises – the dolphins strike the much smaller porpoises, and often bite them with such force that they kill them. It’s still not clear why this happens, but all the observed cases have been by sub-adult male dolphins, so the current theory is that it has some link to sexual behaviour. I had no idea when I used to watch Flipper on television that dolphins could be such violent animals!
In 2015, a Cuvier’s Beaked Whale live-stranded in Scotland, and in spite of several attempts to refloat the animal it eventually had to be euthanised. An underwater necropsy was carried out, and it was found that the poor creature had a large volume of plastic sheeting in its stomach. This particular animal seemed to have some other health problems, which might have brought it closer inshore and resulted in aberrant feeding behaviour. While it might be the case that the ingestion of plastic debris is an increasing problem for cetaceans, Deaville found that there were only 3 cases out of almost 4000 where death was a direct result of an animal eating debris, and 35 cases where debris had been ingested though it was not the direct cause of death. Deaville did flag up that certain species of deep-diving suction-feeding whales could well be more directly affected by plastics, however, but these are whales that are least likely to be recovered for autopsy. He also said that the effect of microplastics was not yet fully understood in cetacean strandings.
He then moved on to infectious disease, which is by far the largest cause of death in cetacean strandings across all species. Deaville has been extensively studying the effect of PCBs (Polychlorinated biphenyls) on cetaceans – although these chemicals are now banned, they continue to persist in the environment, and they accumulate in animals that are at the top of the food chain such as whales. They are immunosuppressant, which might make the whales more vulnerable to infectious disease, and they also affect reproductive success. In studies of PCB levels, striped dolphins, bottlenosed dolphins and killer whales were all found to have toxic levels of PCBs in their blubber, with killer whales being most affected.
Deaville went on to speak about Lulu, a member of the last remaining resident Killer Whale pod in the UK. She was found dead on a beach in Tiree, Scotland, following becoming entangled in creel nets. However, her PCB levels were the highest ever found in any mammal, and her ovaries were non-functional. Lulu’s pod have never had a calf in the 30 years that they’ve been studied, and there is no doubt in Deaville’s mind that that pod will become extinct, and there will be no more coastal killer whales in the UK.
Finally, Deaville went on to talk about cetacean strandings in the Thames. The vast majority of strandings are harbour porpoises (probably about 450 out of the 500 strandings recorded in the past 30 years). However, pelagic species such as minke whales do sometimes find themselves in the shallow seas of the estuary, and unfortunately for them there’s usually only a fatal outcome. However, the Thames is a much healthier environment that it has been historically, and lots of marine mammals make their way up and down the river without coming to any kind of harm.
To conclude, Deaville talked about two high-profile strandings. In 2019 a humpback whale was seen in the Thames. The animal was clearly unwell, and died two days after its first appearance. On investigation the whale was seen to be a juvenile female, and she had been severely injured in a ship strike probably 48 to 72 hours previously. During 2019 there were 3 cases of entanglement and one of ship strike involving humpback whales, and as the population of this species increases it’s likely that there will be more events of this kind.
In 2021 a small female minke whale stranded in the lock at Richmond. An attempt was made to move her but she escaped, and was later found at Teddington lock, the furthest up the Thames that a whale has ever been sighted. She was eventually euthanised, and necropsy showed that she was extremely thin, and probably hadn’t fed for some time – it’s possible that she hadn’t been completely weaned from her mother, and, having wandered into the Thames, wouldn’t have been able to find any alternative food. Again, this is a species which is increasing, so more strandings might reflect more animals.
So, to conclude:
CSI has investigated over 18,000 strandings and has conducted 4500 necropsies.
Although its work is opportunistic (inasmuch as it relies on being able to retrieve stranded animals), it is a cost effective method of looking at threats to the marine environment, and its work is used to create policy, to further the science of cetacean strandings, and to educate and inform.
CSI looks at the anthropogenic causes of strandings, such as bycatch, entanglement, ship strike, noise, climate change and marine debris, and non-anthropogenic causes such as bottlenose dolphin attack.
However, CSI consider that PCB exposure is the biggest single conservation concern for some species, and is a threat to the existence of some populations.
So, an absolutely fascinating talk, and lots that I didn’t know. If you’d like to listen to the whole talk, you can find it here.
Dear Readers, I have always been interested in the history of botanical gardens, and their role in conservation, so this talk by Dr Shahina Ghazanfar intrigued me. Dr. Ghazanfar works for the Royal Botanical Gardens at Kew and her specialisms include the plants of Oman and Iraq. The title of the talk is a little misleading, as the subjects covered ranged much more widely than I expected, but I learned a lot, and that is always a good thing! The talk covers a) the history of plants and human beings, and how they are intertwined, b) the history of botanical gardens in the ancient Middle East and elsewhere, and finally c) the cultural history of plants, and how specific it can be to place. Dr Ghazanfar concludes with thoughts about the role of the botanical garden in the future, specifically to the preservation of a plant’s cultural context.
Dr Ghazanfar began by explaining that plants have always been the companions of human beings: even before agriculture, there’s evidence that favoured plants were carried as seeds and used for medicinal or ritual purposes. But once people became more sedentary, the first gardens were planted, mainly for food – it helped to know where to find key crops, rather than having to spend time foraging.
From Neolithic times (12000 BCE) plants and domesticated animals were moved from their places of origin, to such an extent that it’s now hard to know where some of our key crops actually originated. However, there is evidence that there were food surpluses from about 3000 BCE which drove trade between different parts of the world – East Africa, the Middle East, South East and Southern Asia were already economically involved with one another, and linguistics has been able to show the way that plants from one culture were incorporated into another.
Dr Ghazanfar moved on to talking about Egypt in particular. The Ancient Egyptians believed that the art of cultivation was taught to humans by the gods, in particular Osiris, and the fertile floodplains of the Nile were vital for the survival of the civilisation. Floral collars were an important part of funerary rites – they included olive, which was not native to Egypt but was grown specifically for this purpose. Plant inventories of the time include such plants as tamarisk, pomegranate, myrtle, figs, sycamore, willow, moringa, date and doum palms and carob, most of which are alien species cultivated for particular purposes.
Doum Palm (Hyphaene thebaica) (Photo Two)
Wine and viticulture were known in Egypt and Mesopotamia from as far back as 3000 BCE, and in 128 BCE traders from the areas now known as Central Asia (Uzbekistan, Kyrgyzstan, Kazakhstan) brought vines and wine to China for the first time.
Moving on to botanical gardens, Dr Ghazanfar explained that the first such gardens were physic gardens, for medicinal plants, or were meant to showcase different methods of cultivation. Subsequently they were for pleasure or status, to show off the strange and varied plants that could be grown. It was only in the 19th and 20th centuries that they began to have scientific and conservation importance. However, they have always had a role in preserving history and culture.
The earliest known botanical garden is the Royal Garden of Thotmes (3000 BCE), adjoining the Temple of Karnak in Egypt and planted by Nekht, the head gardener of the temple. It contained vine pergolas and doum palms surrounding a rectangular pond containing lotuses, and was most likely a pleasure garden.
The Ancient Greeks didn’t appear to have botanical gardens, although Aristotle does mention a garden that he left to Theophrastus (270-287 BCE) after his death – Theophrastus subsequently improved it, and left a guide to the 500 plants that it contained.
What, though, of the most famous of the botanical gardens of the ancient world, the Hanging Gardens of Babylon? Dr Ghazanfar explained that these were most likely not in Babylon but in Nineveh at the Palace of Sennacherib, in the north west corner of what is now Iraq. It would have had an extremely sophisticated watering system, as the plants were arranged in tiers. Mostly the plants were grown for their decorative values, but some that provided the more exotic fruits for the palace would also have been grown. Sennacherib was an Assyrian king who ruled from 705-681 BCE, and there are drawings from the garden during the time of his successor, Ashurbanipal, which show the plants arranged in beds. It’s difficult to see what plants were included, but some clearly resemble cypresses and date palms.
Relief of the gardens of Nineveh (Photo One)
At approximately the same time, the King of Babylon also had a garden, and there are cuneiform tablets from this time split into sections, with details of which plants were planted in which bed. Frustratingly, we still don’t know which plants were represented, but it certainly shows a fine degree of organisation.
However, Dr Ghazanfar considers that the Chinese emperor Wu Tai (140-86 BCE) was the creator of the first botanical garden as we would understand it. He sent out collectors not just to other parts of China but right into Central Asia and the Middle East to bring back plants, and is credited with being the first person to cultivate the vine, pomegranate, safflower, common bean, cucumber, lucerne, coriander and walnut in China.
In Spain, gardens in Cordoba, Toledo and Seville built during the 8th to 11th centuries are thought to be the precursors of the Renaissance garden, though they were largely designed to enable agricultural experimentation – during the Al Andalus period there was a great flowering of scientific inquiry by Islamic scholars, and treatises were written on subjects such as the production of linseed oil from flax.
The oldest academic botanical garden that is still in its original location is the Orto Botanico di Padova in Padua, founded in 1545. It represents an understanding of the relationship between nature and culture, and has contributed to many of the sciences, from ecology and chemistry to botany and pharmacy.
Botanical Gardens of Padua (Photo Three)
The Jardin des Plantes in Paris was established in 1635 as the Royal Garden of Medicinal Plants by Guy de la Brosse, Louis XIII’s physician.
In 1673 the Chelsea Physic Garden in London was founded as the Apothecary’s Garden, with the aim of teaching apprentices how to identify and use plants. However, the University of Oxford Botanical Garden is the oldest botanical garden in the UK, founded in 1621 as a physic garden but now one of the most compact yet diverse collections in Europe: in only 4.5 acres it contains representatives of over 90% of all known plant species, and I personally recommend a visit if you’re ever amidst the dreaming spires and need a break.
When people think about botanical gardens in the UK however, their thoughts are inexorably drawn to Kew. Founded in 1759 by Princess Augusta, mother of George III, it didn’t become a public garden until 1841. The director, William Hooker, greatly expanded the area of the gardens from 10 to 75 acres, commissioned the famous glass houses, and set up a museum of economic botany. By his death in 1865 Kew was a leading scientific institution.
Some of the key botanical introductions at Kew were the Ginkgo, first planted in 1762 (and this original tree is still growing well today), and the Pagoda tree (Sophora japonica). This latter tree is actually native to China, not Japan, and one of the original trees still survives. Five were imported to the Duke of Argyll’s estate in 1753, and this tree was transplanted to Kew when still a sapling in 1762. It’s one of the few plants that survives from Princess Augusta’s original garden.
Pagoda tree in Kew Gardens (Photo Four)
Kew has had an important role in the conservation of many endangered plants. The smallest water lily in the world, the Rwandan Pygmy Lily (Nymphaea thermarum) disappeared from the wild after its habitat was destroyed – this is the world’s smallest water lily, with flowers less than 1 cm across. Fortunately the botanists at Kew were able to grow some of the plants from seed. At the other end of the scale, the titan arum (Amorphophallus titanum) grows a frankly embarrassing flower some three metres tall, more or less when it feels like it – its flowering was described by Dr Ghazanfar as ‘rare and unpredictable’.
Dwarf Water Lily (Nymphaea thermarum) (Photo Five)
Titan Arum in flower (Photo Six)
In India, there are many important botanical gardens, but to mention two: the Acharya Jagadish Chandra Bose Indian Botanic Garden(founded in 1787) in Kolkata is famous for its 250 year-old banyan tree: banyan trees grow by expanding via aerial roots, and this tree now covers some 4 acres. The Government Botanical Gardens in Ooty, founded in 1848, is a high-altitude garden which was a pioneer in growing many medicinal and food plants in India, most notably Cinchona from Peru, which is the source of quinine for the treatment of malaria.
Dr Ghazanfar moved on to talking about the relationship between a plant in its native habitat and its culture, and how the connection is often lost when a plant is cultivated elsewhere. She also described how, with climate change, some plants can no longer survive in their original environments. She sees a role for botanical gardens in preserving these links.
The Date Palm, for example, is mentioned extensively in both the Koran and the Bible. In the Koran the plant is described as a source of food, fibre, shade and enjoyment. Medicinally, it is thought to help with childbirth, and the Koran specifically mentions the importance of conserving the plant. In Islamic thought, it symbolises wisdom.
In the Bible, the Date Palm symbolises holiness, resurrection, justice, righteousness and honour, and many place names derive from the sites of Date Palm groves.
In Hinduism there are five sacred trees mentioned in the Vedas – Cannabis, which is associated with Lord Shiva, Tulsi, Sandalwood, Jasmine (also identified with Lord Shiva), and Neem or Indian Lilac, associated with the Goddess Durga.
Pomegranate is another plant associated with both the Koran and the Bible: in the Koran it is seen as a blessing and as a symbol of paradise, as an exhortation not to be wasteful and to share equitably. In the Bible, it’s a symbol of feminine beauty. However, it has been a symbol of prosperity, fertility and rebirth in both the Jewish and Ancient Egyptian religions, and was recommended by the Prophet Mohammad as a fruit that purged the body of hatred and anger. Pomegranates are grown in many, many places now, but in so doing they lose the depth and breadth of cultural associations that they had originally.
Dr Ghazanfar concludes by saying that botanical gardens in the future could include the cultural significance of the plants in their collections as well as just their medicinal and culinary uses, so that these would not be lost in future, which seems like an excellent idea to me.
Photo Three by By By A. Tosini – G Agostini “dis. in. pictra” – lithographed by “Kiev”? in Venice – older version uploaded by User:Esculapio – Unknown source Reprinted in “L’Orto botanico di Padova nell’ anno 1842” by Roberto De Visiani (1842), Public Domain, https://commons.wikimedia.org/w/index.php?curid=518901
Dear Readers, this is a topic that will be close to all of our hearts, I’m sure. Are we actually helping birds when we feed them in our gardens? Should we be doing it all year round? What are the pitfalls of attracting large numbers of birds to a small space? I was eager to hear what Mike Toms had to say – he wrote the ‘Garden Birds’ volume of the New Naturalist series, one of my favourites, and currently works at the British Trust for Ornithology (BTO), so he’s a man who knows of which he speaks. I’ve given quite a lot of detail here as I found it absolutely fascinating.
Toms started by explaining that the BTO is a research-based organisation that looks specifically at bird populations – changes in distribution and numbers, and the reasons for those changes. The bird that has been studied the longest is the grey heron – BTO have data going back to the 1930s and were able to map a correlation between cold, hard winters and declines in the heron population. Increasingly, though, the BTO studies birds in urban environments. In 2008 the world reached a point where half the population now lives in towns and cities, and this is expected to increase to two-thirds of us in 2050. Urbanisation has consequences not just because of the footprint of the areas themselves, but because of the resources that are needed to support them. Globally, some of the areas that are urbanising most rapidly are also those with the highest current levels of biodiversity, such as south-east Asia and the Horn of Africa.
In the UK, some species can adapt very nicely to the urban environment (Toms showed a photo of two herring gulls looking hopefully at somebody sitting on a bench with a sandwich). Such species have a broad diet, and are not too specific in their requirements, which is one reason why dove and corvid species do so well in our towns and cities. In the garden environment, you’re likely to see a lot of seed eaters, such as sparrows and finches, but far fewer insectivores.
London is particularly well-blessed with green space, however, and although we think about this in terms of parks and woodland, private domestic gardens are by far the biggest space. Taken together, the gardens of the UK cover a larger space than all of the land set aside for nature reserves. At this point, Toms did a survey on whether the live audience thought that gardens were good for birds, and over 90% thought that they were.
Toms then started to look at gardens in more detail. One trend, especially since lockdown, was that people wanted to make their little bit of greenspace more wildlife friendly – he showed a slide of a garden from the Chelsea Flower Show which was contemporary but had a bird feeder, lots of pollinator-friendly plants and some small trees and shrubs – it seemed like a nice combination of the aesthetic and the useful.
The big draw for birds in our gardens is clearly food – Toms had the staggering figure that across the UK we spend £200m per year on bird food (and about half of that is me 🙂 ). For birds to stay in our gardens, and not just use them for food, there need to be nesting opportunities too.
Toms showed an interesting graph which illustrated the reporting rates for robins – volunteers at the BTO record which birds they see in their gardens every week. It showed firstly that reporting rates for rural and suburban gardens are higher than those for urban gardens overall, but that all three types of garden showed a drop off during the breeding season – this seems to indicate that while robins will use gardens during the winter season as a food resource, they prefer not to nest in them.
Why is this? One reason is that most birds feed their nestlings on insects, and these are just not plentiful enough in gardens. Blue tits, for example, will nest in deciduous woodland where there are lots of caterpillars given the choice. This year was particularly devastating for birds as May was so cold, and June so wet, so there were lots of reports of nests failing and nestlings starving in the nest. However, a significant proportion of birds (over 50% of starlings and sparrows, a third of jackdaws and blackbirds and, surprisingly, 25% of song thrush) do breed in gardens, so the habitat is clearly important for these species.
Rural gardens in particular can also be important for birds such as the yellowhammer, tree sparrow and reed bunting, who are seedeaters – Toms showed a graph of farmland birds who visit gardens with a seasonal peak in April, when all the natural food that the birds would normally eat has finished. In days gone by, there would be grain amongst the stubble, but with more efficient farming methods, the birds have taken to visiting feeders. This is especially important in the case of the cirl bunting, a very rare species in Devon, where garden feeding has really helped to reinforce the population.
Turning to blackbirds, Toms showed a graph of the reporting rate of the birds which showed a marked fall-off in the autumn every single year. He explained that this is partly due to the birds becoming more secretive during the moult, but also that they often move out of gardens during the glut of berries that are available in parks and the countryside.
With blue tits, Toms spoke about ringing exercises (where individual birds can be identified), which shows that it isn’t just the same old three or four birds visiting the feeders, but a succession of birds – you could have thirty different blue tits visiting the feeder in the course of a day.
Toms moved on to coal tits – these little birds largely feed on the seeds of coniferous trees, and so have done very well with the planting of sitka spruce plantations (one of the few creatures that have, I imagine). Again, the data from the recorders showed an annual peak and trough, but the peak was supressed in years when the spruces were ‘masting’ (producing their seed) – this only happens every few years, so that there is so much seed that the predators can’t eat it all, and the tree has the best chance of reproducing. In other words, if the spruce seed is available, the coal tits will eat it in preference to visiting the garden, but they will use the gardens if it isn’t so plentiful.
Then, Toms looked at longer term studies. One of them, on goldfinches, has showed a massive increase in the use of gardens by the species. Interestingly, there seem to be two ‘spikes’ in the data, which might indicate that firstly resident birds are using the gardens for food during the breeding season, and then a second wave of migrant birds comes in to take advantage of the resource.
Feeding is not an unalloyed good, however – Toms gave the example of trichomonosis and the greenfinch. This protozoal parasite is spread in saliva and faeces from infected birds, and is a very good reason for making sure that feeders are cleaned regularly. What I hadn’t realised was that the ‘spillover event’ probably came from woodpigeons, who have been carriers of this parasite for years, and one place where pigeons and greenfinches come into contact is at seed feeders in gardens. Greenfinch and chaffinch populations have been horribly affected, with Toms describing the chaffinch population as being ‘in freefall’. It made me think about the last time that I saw chaffinches in the garden, and it’s been quite a while ago.
The ‘pox’ that we sometimes see on blue and great tits seems, according to the BTO research, to have actually come from blackflies which have jumped across from the European mainland, thanks yet again to climate change.
Finally, Toms looked at blackcaps. These birds are increasingly using our gardens in the winter time (probably migrating in from Eastern Europe), and interestingly they prefer urban gardens, which are warmer because of the urban heat island effect (all that concrete stores heat during the day and releases it at night, increasing the ambient temperature). Blackcaps also prefer gardens where food is available every day.
So, it seems that the food that we provide is changing the behaviour of some birds, but by attracting them to our gardens we also increase their exposure to some diseases, and to different predators, such as cats and grey squirrels, which might not be so common in the countryside.
So, what were the conclusions? It’s very clear from the BTO’s studies that the birds who are visiting our gardens have become more diverse over time. We’re also putting out different foods – many of us are feeding not only seeds and peanuts, but suet products. Apparently, too much fat can affect a bird’s feather condition, but the addition of Vitamin E can counteract that. Where do I get suet products with Vitamin E, I wonder?
Living in an urban area brings a whole selection of risks and opportunities. There is pollution in cities that especially affects birds with their delicate lungs, glass windows claim billions of bird lives globally every year, and night time lighting can be confusing and destructive. Some studies have shown that blackbirds living in urban environments have shorter telomeres (the sections of their genetic code that protect the core genes), indicating that they have increased stress levels. Robins have to sing at night because they can’t make themselves heard over the traffic noise. Woodpigeon populations have gone through the roof, and may be contributing to disease in other species.
To sum up, Toms indicated that gardens are probably good for birds on balance, because they provide feeding opportunities and help to offset some of the damage that humans have done elsewhere. But it isn’t straightforward. Toms put in a plea for more research on what birds need, and especially pointed out the BTO’s Garden Bird Watch
Dear Readers, every gardener or natural history enthusiast that I bump into has something to say about the way that plants are changing their habits. So often, though, the information is anecdotal, because we don’t tend to actually record things when they happen. So, it was wonderful to attend this talk by Alastair Fitter, son of Richard Fitter, who wrote the first book about London’s wildlife in the New Naturalist series back in the 1940s and who was, among many other things, president of the London Natural History Society. From 1954 to 2000, Richard Fitter recorded the first flowering dates of various wildflowers growing in his garden and this produced a data set that turned into the first major study of the impact of climate change on the flora of the UK. That document was published in 2002, a collaboration between Richard and Alastair Fitter, when Fitter Senior was nearly 90 years old. The Fitters were interviewed on Radio Four’s Today programme, and when Richard was asked why he’d done all that recording, he replied that as a boy he’d been told that it was always good to write things down. As Alastair Fitter remarked, thank goodness he did!
Another very useful resource is the Woodland Trust’s ‘Nature’s Calendar’, which recorded ‘First Flowering Days’ for a selection of different plants between 2001 and 2016.
What is very clear is that plants are coming into flower earlier, and that this process has speeded up over the past 25 years. From the Woodland Trust data, we see that:
Hazel (Corylus avellana) produced its catkins 31 days earlier in 2016 compared to 2000.
Hazel (Corylus avellana) (Photo One)
Lesser celandine (Ficaria verna) has advanced its flowering date by 27 days between 2001 – 2016, but Richard Fitter recorded the flowering had already come forward by 20 days between 1954 and 2000, making a total advance of an astonishing 47 days between 1954 and 2016.
Lesser celandine (Ficaria verna) (Photo Two)
English bluebells have advanced their flowering date by three weeks since 2001.
English bluebell (Hyacinthiodes non-scripta) (Photo Three)
From Fitter’s data, if you took all the different species in the sample, there had been a general movement towards earlier flowering of about 6 days by 2000, but this hid some major movements by individual plants. For example, white deadnettle (Lamium album) flowered 55 days earlier in the 1990s than it had in the 1950s (and indeed now flowers all year round).
White deadnettle (Photo Four)
There are some very strange anomalies, however: our old friend Buddleia flowered a whole 36 days later in the 1990s compared to the 1950s, and it’s still unclear why. All theories duly considered!
Butterfly Bush (Buddleia davidii) (Photo Five)
And while we’re on the subject of garden plants, Fitter describes how Fred Last studied his garden and recorded first flowering dates from 1978 to 2007. Mahonia advanced its flowering time during this period by an extraordinary 3 months (which now makes it one of the handiest garden plants for early bumblebees).
Mahonia japonica (Photo Six)
More recent data comparisons by Alastair Fitter show that over 50% of plants are coming into flower by the end of April, an advance of about 5 weeks. But the question is, why?
Fitter explained that flowering times are determined by a number of factors. Firstly, there’s the question of when the flower buds form. For spring bulbs, next year’s flowers are formed during the previous summer, but the actual flowering time is determined by the temperature in the spring. Fitter used the example of the Tulip Society shows to illustrate this. The date of the Wakefield and North of England Tulip Society’s annual show is determined by when the ‘English florist tulips’ are thought to be coming into their best. The Society was founded in 1836, and Fitter showed a lovely slide, where the date of the show has been coming forward on a smooth curve that exactly matches the average mean temperature in March: for every degree increase, the show comes forward by three days. The show is now commonly held in the second week of May, compared with the very end of May in the mid 1800s.
Tulips at the 181st Wakefield and North of England Tulip Society Show (Photo Seven)
Another factor that determines flowering time is day-length, with some plants coming into flower as the days lengthen, and others as the days get shorter. Fitter points out that for the majority of plants, we simply don’t know how day-length affects them but for a few, such as red campion (which responds to lengthening days) and hops (which react to shortening days) we can see a correlation.
Temperature is, however, critical. Fitter showed how the flowering time of Coltsfoot was dependent on the mean temperature in February but, more generally, an increase in temperature of 1 degree in the four months before flowering could advance the flowering date by about three days. However, a warm summer and autumn could act to delay flowering by about the same amount. Go figure! I wondered if a warm summer and autumn might mean lower rainfall, which could delay bud formation. What is clear is that a lot more research is needed, and there is still a lot that we don’t know. The pattern is clear, however: most plants are flowering earlier, and flowering patterns are becoming a lot less predictable.
Coltsfoot (Tussilago farfara) (Photo Eight)
Fitter’s final point was, do these earlier flowering times matter? And of course, there are a number of problems not just with earlier flowering, but also with the increased unpredictability of flowering times. Some pollinators, for example, will take advantage of earlier flowering, but where there is a very specific relationship, such as that which occurs with orchids, the plant may come into flower but the pollinator will not yet have emerged. Sometimes, as in the case of the orange-tip butterfly, the insect is responding to earlier flowering times of cuckooflower, so that its caterpillars, which feed on the seedpods of the plant, are still ‘in sync’.
However, something that had never occurred to me was that, as flowering times change, some plants will be more or less likely to hybridise because their flowering times will move further apart, or begin to overlap. Sweet violets (Viola odorata) will be less likely to crossbreed with hairy violets (Viola hirsuta) because their flowering times are now 15 days further apart. Red campion (Silene dioica) and white campion (Silene latifolia) are, however, coming closer together, and so hybridisation is more likely. As Fitter points out, hybridisation is a major driver of evolutionary change, and so some groups may become less able to adapt over time as their flowering times grow further apart.
Hybrid Campion ( red campion (Silene dioica) and white campion (Silene latifolia) (Photo Ten)
And so, Fitter ended by saying that earlier flowering times are a clear harbinger of climate change, and an indicator that things were changing rapidly in the natural world. We owe a debt of gratitude to Richard Fitter for ‘writing things down’, and it seems to me that this illustrates yet again the importance of citizen science, of recording these extraordinary times that we live in. And Fitter finished as he’d started, with a quote from Shakespeare, in which Titania blames Oberon for the strange changes in the climate. I think we need to look a little closer to home.
‘And thorough this distemperature we see The seasons alter: hoary-headed frosts Far in the fresh lap of the crimson rose, And on old Hiems’ thin and icy crown An odorous chaplet of sweet summer buds Is, as in mockery, set: the spring, the summer, The childing autumn, angry winter, change Their wonted liveries, and the mazed world, By their increase, now knows not which is which.’
I cannot recommend this talk highly enough, and you can watch the whole thing here.
Dear Readers, when I hear the phrase ‘Human/Wildlife Conflict’ I think of villagers fighting off elephants who are raiding their crops in Sri Lanka, or oil plantation workers chasing orang utans with machetes. But there are plenty of occasions in the UK when our hard-pressed wild creatures come into rather more contact with humans than is good for either party. I do love a talk that makes me think about something that I’d never considered before, and so it was with this one. Claire Boothby, who works for the organisation ‘Bats in Churches’ has the remit of trying to mitigate the problems that occur when bats roost in churches, and she had some very interesting things to say on the issue.
Bats have always used churches as roosts – they seem to prefer older churches with wooden roofs. One conservationist suggested that those timber beams reminded the bats of ancient woodland, which is where they would probably roost preferentially if there was enough of the habitat left. If the church is surrounded by a nice big churchyard with lots of flying insects, so much the better. In the summer, the female bats like the warmer part of the church as it’s ideal as a maternity roost. In the winter, they may favour places like crypts and undercrofts as hibernation sites.
Many churches have voids in the roof with direct access to the outside world, and in these cases the parishioners might not even know that there is a bat roost. The trouble comes if the bats have access to the interior of the church. My heart is obviously with the bats, but Boothby showed how the droppings from the bats can damage brass memorial plaques, marble tombs and stained glass windows. Many of the volunteers who clean churches are elderly, and the church can lose significant income from weddings and events if the building is soiled. One church in the study closed because of the damage from a substantial bat roost.
What to do? The bats are protected (thank goodness) but the buildings are part of our heritage, and are often also the centre of a small community. Fortunately, Bats in Churches works with all the parties involved. Funded by the National Lotteries Fund, it brings together the Bat Conservation Trust, the Church of England, Historic England and the Church Conservation Trust, and it works very closely with the parishioners and clergy at the church.
It’s easy to demonise those in the churches who are complaining about the bats, but in the video interviews with them, they were all quietly apologetic about even mentioning the problems that they were experiencing. They wanted to conserve the bats, but they were also worried about the churches, one of which was an extremely rare brick-built Tudor church. They were also worried about the cleaning burden that fell on a group of volunteers who might scrub for hours only to find that, when they returned a few days later, things were just as bad.
St Nicholas, Chignal Smeally (Photo One)
So, what to do? In churches where the bat population wasn’t causing too many problems, such as Holy Trinity Tattershall, the bats were turned into a feature, with a bat information board inside the church, bat walks outside it, bat teeshirts and a ‘Tatty Bat’ mascot that people could buy.
‘Tatty Bat’ merchandise from Holy Trinity, Tattershall (Photo Two)
In churches where the problem was worse, however, there were capital works on the building. Bat surveyors would get an idea of the size of the roost, the species involved and their entrance and exit points. They would be watched to see how they were behaving, and then a plan was drawn up that would minimise the damage in the church without affecting the bats. In some cases, this could involve something as simple as a screen so that when the bats left the roost they were funnelled towards the outside exit, rather than flying around in the church first. In another, a bat box with heraldic symbols on it was created so that the bats had a perfect roost with the same entrance as previously. In the most expensive example, St Lawrence Radstone church had so many bats, and so many droppings, that the church had actually been closed. Part of the church had a twelfth century ceiling, but the bats were in the much later Victorian part of the roof. A plan was drawn up to create a false ceiling in the Victorian bit, so that the bats still had a void to fly around in, but could enter and exit from their original points. This was so successful that the church was able to reopen in 2020, without any damage to the bats. You can watch a video about the project here.
St. Lawrence Church, Radstone (Photo Three)
All of the projects mentioned are subject to monitoring for at least three years, and hopefully longer, to ensure that the bat populations haven’t been harmed by the changes. I must say that I was impressed by the imagination and dedication shown by all parties, who clearly wanted to achieve a solution.
Bats in Churches would really like some help surveying churches: you don’t need to be a qualified bat surveyor, and it sounds like an interesting and worthwhile project. They are trying to survey a sample of 1000 churches (they ground to a halt during the pandemic along with everybody else) and, excitingly, you get the loan of a bat detector and are taught how to submit bat droppings for DNA testing. Who could resist? If you think you fancy it, all the details are on the Bats in Churches website here.
Claire Boothby was a very engaging speaker who is clearly passionate about finding solutions to the tricky problems of bats, people and medieval buildings. It was a real pleasure to watch her talk, and if you’d like to do the same, you can find it here. These LNHS talks have been so fascinating and varied that I hope they continue even after the pandemic – it’s clear that they can reach and educate a much wider audience than their London evening in-person events did. Fingers crossed that we can soon have both!
Dear Readers, as you will know I am a great fan of our urban foxes, and so I was looking forward to this talk very much. Prof. Scott did one of the earliest and most extensive studies of urban foxes in Bristol, and much of what she found has greatly informed our understanding of these animals.
Prof. Scott is very interested in how animals adapt to urban landscapes, and why some do better than others. She describes cities as ‘landscapes of fear and opportunity’. The opportunities include that cities are warmer, there are less predators, more food (especially as people deliberately feed year-round), lots of niches for refuge, and consistent water supplies. There is, however, less natural food, more competition, a higher risk of disease as territories tend to be smaller, danger from the roads, from some pets, and also, of course, a high risk of conflict with people. The animals that tend to do best are enterprising generalists – this includes foxes, but also badgers (who are increasingly being seen in the suburbs) and hedgehogs (who are now commoner in urban areas than in many places in the countryside).
Prof. Scott described how adaptation to city life for an animal usually includes an increased density of animals (as there are more food resources), higher aggression (because of competition for those resources) and much less fear of humans – this is known as ‘synurbanisation’. She considers that the extraordinary ability of the fox to navigate the 3-dimensional structures of the city to be one of its key skills in making the city its home – she tells of finding foxes living on roofs and in trees. Anyone who has seen a fox effortlessly bound over a six-foot fence will be nodding their heads in agreement.
Prof. Scott believes that an understanding of the fox would help to offset some of the hostility that people feel towards the animal. Socially, foxes tend to live in groups of 3 or 4 – typically a small ‘family’. However, foxes forage for food on their own once they’re into adolescence. They communicate mainly by smell, which explains the piles of poo and that heavy ‘foxy’ smell that they produce – it’s thought that the scent messages might include sex, breeding status and even dominance. As anyone who has been woken up in the night also knows, foxes communicate by sound too – there are over 28 different calls, including the screaming of vixens, the barking of dog foxes and the various bouts of yipping that can enliven many an early morning. However, the screaming is only likely to be heard in December – February, when the vixens are in heat and, apart from a lot of chaos when the cubs leave the den in May, foxes are generally fairly quiet for the rest of the year. Females will have a natal den where the cubs are born (frequently under a garden shed it seems), but they will move the cubs if disturbed, and adult foxes will have several rest sites in their territory where they hide during the day. They are largely, but not exclusively, nocturnal, as the foxes who turn up in my garden will attest.
Only one in five foxes will live to be two years old, with roads claiming the majority of victims. In captivity, foxes can live ten to fourteen years on average.
On the vexed question of whether we were becoming ‘overrun’ with urban foxes, Prof. Scott looked back through the records, and had done several scientific studies of her own. Her view was that urban foxes had certainly spread – in the 1980’s, 91% of cities had no urban foxes, but now most of them did, with the foxes spreading north and west. Her study in Bristol showed that there were approximately 36 foxes per square kilometre. However, in 2010 a devastating outbreak of mange killed 95% of the foxes in the city.
Prof. Scott showed several photos of foxes, some with mange, some who were simply shedding their winter coats. One way of telling is obviously bare, sore flesh, but a real giveaway seems to be if the tails are looking scratty – this is a clear sign of mange. Healthier foxes seem to be able to just shrug it off, but for foxes already weakened by bad nutrition it can be a death sentence. Furthermore, there’s no easy solution: the jury is out on the homeopathic solution that can be given without harm (and possibly without any positive effects either) but the normal veterinary treatment can only be given under controlled circumstances. Furthermore, Prof. Scott found that foxes who were taken into sanctuaries for treatment and then released back into their old territories nearly always found that a new fox had taken over their old home, and the original incumbents were usually driven out, with all the concomitant dangers of being run over as they searched for a new territory. Prof. Scott’s opinion was that, hard as it seems, mange is something that limits the numbers of foxes in an area when they get too high – it thrives in conditions where there are lots of foxes in close proximity. A more ‘usual’ population of foxes seems to be about 12 foxes per square kilometre, something seen in more recent studies in Bristol (post mange) and London.
High concentrations of foxes are often supported by feeding. In a recent study, Prof. Scott found that 36% of the people in her study fed foxes, mostly either by hand or at the back door. One fox in the study spent his whole time waiting outside the house where he was fed at 8 p.m. and then moving to house number two where he was fed at 10 p.m. There are issues around what was fed (foxes definitely like jam sandwiches but are unlikely to make them for themselves), and the danger of allowing foxes to associate people with food. Some of the more lurid headlines seem to feature foxes who feel perfectly comfortable going into people’s houses and making themselves at home, often biting people when cornered. Prof. Scott’s advice is to feed little, feed something appropriate (like dog food) and not to feed too close to the house, and certainly never by hand.
And finally, one of the questions that Prof. Scott is frequently asked is ‘do foxes kill cats?’ Well, we’ll never know for sure that there isn’t a rogue fox out there with a taste for felines, but judging by the trail camera evidence, a solitary cat can see off two foxes who attempt to snaffle her tea. Apparently in all the filmed incidents, the cat beat up the fox. Badgers trump foxes and cats, however, although there was no evidence that badgers actually hurt cats. One film clip showed a hedgehog feeding, at which point a fox picked it up and deposited it elsewhere before coming back to eat the food. It’s easy to see that that’s a situation that could lead to the fox predating the hedgehog.
So, this was a very interesting talk, with a lot of thought given to how people and foxes can live together more harmoniously. Prof. Scott thinks that understanding the fox is key, and I agree – as with everything, knowing the reason for something (such as night time screaming or piles of poo) can make it a lot more bearable. I for one love to see the touch of wildness that the fox brings, and am happy to put up with a little inconvenience for the pleasure of their company.
You can watch the whole of the talk here. Highly recommended.
A young vixen in St Pancras and Islington cemetery. My favourite British wild mammal.
Dear Readers, the London Natural History talk this week was of particular interest to me. When we had a bird survey done in 2019, Coldfall Wood was found to be particularly rich in breeding birds for an urban woodland, but the increased footfall during lockdown, coupled with the threats to the environment itself, have made me worry about the additional pressure that is being put on the animals and plants that live there.
Jeff Waage was part of a team that undertook a survey of Hampstead Heath last year. Part of the reason was to determine which birds were displaying breeding activity, and where: disturbance from walkers and dogs is widespread even if there isn’t a pandemic, and there has been an increased demand for Forest Schools, ‘Forest Bathing’ and professional dogwalking. In the past year the Heath has had an estimated 50 million visitors, which is pretty much equivalent to most of the population of the country popping in. But data can help, and so Waage and his team walked transects of between 1 and 3 kilometres through the Heath on at least six occasions, looking for breeding behaviour.
Kenwood, Hampstead Heath (Photo One)
Breeding behaviour was defined as territorial singing, birds carrying nesting material or food or fecal sacs, birds actually sitting on a nest, territorial disputes or sightings of fledglings. In my experience birds are very good at hiding nests, but you can fairly easily spot them ‘eating for two’ (or a dozen in the case of blue tits).
At the end of the survey, there had been 2169 sightings of 41 species of bird. Compared with the 26 species seen in Coldfall Wood this probably sounds pretty good, but the Heath has a much wider range of habitats. However, it’s clear that the Heath’s biodiversity has been under stress for some time: in 1992, a survey revealed 71 species. Many of those lost have been ground nesting birds, who are always the first victims of too much footfall and too many dogs, but even birds such as the mistle thrush and the common whitethroat appeared to be in decline.
Common Whitethroat (Curruca communis) (Photo Two)
Waage estimated that 40% of the Heath’s bird species were red or amber listed: he explained that this designation was arrived at by looking at both the vulnerability of the species (i.e. was it nesting in an area of high disturbance) combined with its ‘patchiness’ (i.e. were there just a few isolated populations within the Heath). For example, the whitethroats nested in scrubby areas where there was a lot of picnicking and dog walking, and there appeared to be only one pair of sparrowhawks.
The approach to maintaining and increasing the bird biodiversity of the Heath was multi-pronged.
Firstly, there was a need to identify areas of the Heath where there would be the least impact on breeding birds for commercial activities such as the forest schools, and this was possible following the survey.
Secondly, where birds were vulnerable there was to be a bid to raise public awareness, through new signage and articles in local newspapers.
A third area was to improve and even create habitat, such as reed beds for reed buntings.
Finally, resources such as food and nest boxes could be made available.
There was also a need to investigate what was happening on the fringes of the Heath – there were surprisingly few nesting finches, for example, and the group felt that this was probably because the finches were nesting in local parks and gardens instead, where there was a higher availability of food.
And lastly, and probably most importantly, the Heath needs continued monitoring to see what’s happening with the bird populations. Data can be our most powerful tool in gaining an understanding of what’s happening in an area, and over time. It will be interesting to see what future surveys reveal.
I’ve always been very happy to just enjoy nature, and to be thrilled at the arrival of a new bird or the sight of an unexpected insect. I’m still thrilled, but it seems to me that collecting data is a way of putting meat onto the bones of the anecdotal picture that you build up over the years. Citizen science is becoming increasingly popular, and I hope that, just as the Big Garden Birdwatch has become a major way of recording trends in garden birds, so other surveys will build up a picture of what’s going on with other plants and animals. In fact, there’s an online conference on this very subject being run by the Field Studies Council in May, with the added bonus that it’s concentrating on urban wildlife recording. I’ll be there, and will report back, but for £5 it seems like a bargain for anyone interested in getting involved with recording. With habitat destruction and climate change in full swing there has never been a better time to take notice of what’s going on around us.
Dear Readers, can I start by saying that this was a fascinating and well-presented talk, with lots of fascinating videos and graphics, and if you have an hour to spare I would hot-foot it over to the LNHS Youtube channel to watch the whole thing. Steve Portugal is such a clear and entertaining speaker that it’s best to get this info direct, but here is my synopsis.
The talk is really about why birds gather in groups, how they behave when they do, and what advantages they gain from their behaviour. There are two main ways of ‘flocking’, and these are dictated largely by size. A bird that is smaller than a black-headed gull is likely to form a ‘cluster’ – we see this in pigeons and starlings and all those other little birds. Any bird larger than this is likely to fly in a V-formation, so that includes cranes, geese, pelicans, flamingoes and, as we’ll see, ibises.
To start with, Portugal looked at birds that fly in a V-formation. Partly this might be because large birds are much less manoeuvrable – a crane has the same turning circle as a jumbo jet, apparently. Other reasons might be:
the dilution effect – if lots of birds fly together, an individual is less likely to be predated (this applies to cluster flocks too)
Navigation – older, more experienced birds fly at the front to teach the younger birds behind the route.
Vision – it’s easier to see the lead bird if you fly in a V formation
Energetic – birds are able to save energy by flying in this way.
It’s this last point that Portugal is most interested in. When a plane or a bird flies, it pushes the air in front of it out of the way. At the wing-tip something called a wing-tip vortex is created, and this provides an updraft, which makes staying in the air easier. However, most of the air gets pushed down and creates a downdraft, which will push anything following down. It’s this effect that dictates the gap between planes when taking off at an airport, and its the wingtip vortex effect that is thought to be one of the reasons why birds fly in a V formation.
Lest you think that this is all about birds, Portugal explained that aircraft manufacturers are desperate to copy this effect, to save fuel. He showed a short film made by an airline in which a plane takes off from Melbourne and is joined by others from other Australian airports to fly across the Pacific. When the planes join, they get into a V formation, and fly together until they make landfall above the US, at which point the planes peel off to go to their different destinations. However, another film showed a group of small planes trying to do just this, and getting into all kinds of trouble – planes have to get so close together to find the updraft from the wingtip that they risk stalling or tumbling over. It’s thought that only a computer will be able to calculate the manoeuvres required with enough accuracy to avoid disaster.
The Red Arrows display team in a V Formation. Not as easy as it looks! (Photo One)
However, back to the birds. Portugal’s subject study was made possible by the advent of biologgers that are small and light enough to attach to a bird, and also by a study into the Waldrapp Ibis (also known as the Northern Bald Ibis). Historically they were present all through Mediterranean Europe, Northern Africa and the Middle East but, after the recent extinction of the Syrian population, the only wild birds left are in Morocco. This population doesn’t migrate, but it was hoped that they could be trained to return to their old haunts and establish new groups in Europe. To do this, the birds were given a human foster parent, who lived with them for nine months. Then, they were trained to fly after a microlite, and were eventually taught a migration route to Northern Italy.
Waldrapp Ibis (Geronticus eremita) (Photo Two)
What Portugal found was that these birds, who had human ‘parents’, automatically formed a V Formation when they flew, at 45 degrees to one another, approximately 1.2 metres apart. This was exactly as predicted by aerodynamic theory, which is based on fixed-wing planes. What the birds did was synchronise their wingbeats naturally to avoid generating turbulence between them. Each bird except the one right at the front rode on the updraft of the bird in front.
The group was dynamic, with no clear leader, though birds did seem to have a preference for their position, be it to the right or left, front or back.
However, the birds noticed how long another bird took at the front of the flock, and would then allow it to take a rest at the back, as if they had an innate sense of fairness.
What happened in the flock also depended on the ‘popularity’ of the individual bird. Portugal defined this as ‘the number of connections and interactions’ that a bird had with other birds. If an ‘unpopular’ bird stopped off for a rest, the others would look round, notice who it was, and then just keep going. If a ‘popular’ bird stopped, however, all the other birds would go down for a rest too. What we think of as ‘leadership’ might just be about a network of relationships instead.
Waldrapp Ibis in flight (Photo Three)
Portugal finished his talk with something a bit closer to home: pigeons. Pigeons are about the maximum size for birds that fly in a cluster, and, unlike V Formation flying, being at the front of the group is good from an aerodynamic point of view, being at the back is bad.
Sadly, in pigeon society the popular/unpopular thing plays out in a different way. Shy pigeons are nearly always at the back. Bold, investigative pigeons are nearly always at the front. And unlike with geese and cranes, that’s the way it stays – if you’re a backmarker, that’s where you’ll stay.
Portugal had his pigeons fly over a number of routes. To start with, the group would be somewhat inefficient, but after a dozen flights they’d have the most direct route mapped, and that would be the one that they’d always follow. However, here’s the rub. After the flock had flown a route over a hundred times, he would take pigeons out for a solo flight. The ones who were always at the front came home pretty directly (though interestingly the flock as a whole always flew faster than a solo bird). But when he released a bird that had been at the back of the flock, they almost always either gave up and went to sit in a tree, or got lost, sometimes for days.
Were they just not paying attention? Or were they so intent on keeping up that they didn’t have the energy to see where they were going? Could they maybe not see the lead bird properly? All very good questions for which we have no answers. But how fascinating! I learned so much from this talk, and in particular I loved the clear structure, which makes it so much easier to take in and to remember – I’ve barely had to look at my notes while I’ve been writing this. Do pop over and have a look. I guarantee that you won’t be disappointed.
Dear Readers, this talk exemplified why I am loving this series so much. James Heal is such an enthusiast that although I knew next to nothing about plant galls at the beginning, by the end I was desperate for spring to come so that I could go out gall-hunting. Heal endeared himself to me greatly by saying that he had a dream of giving up his job in finance so that he could become a gall-mite specialist. Who wouldn’t rather be a gall-mite specialist is my question, and I’m an accountant too. But let’s see first of all what a gall is.
We’ve all probably seen plant galls, even if we haven’t been aware of it.
Silk button spangle galls on oak (Photo One)
A gall is abnormal growth on a plant under the influence of another organism. So the ‘silk buttons’ above are actually created by the plant itself, due to chemicals produced by the invading organism. The gall involves the enlargement or proliferation (or both) of the cells or vascular tissue of the plant. This is produced for the nutrition and protection of the gall-inducing organism.
Knopper gall on oak (Photo Two)
The great thing about galls (or one of the great things) is that they can be used to identify what caused them. Gall midges, for example (of which more later) are extremely difficult to identify to a species level from the insect, but the galls can be diagnostic.
So, how do you know what gall you’re looking at? Heal suggested a three-part approach:
Firstly, identify your plant. This might seem easy (‘It’s an oak’) but what kind of oak is it? There are some galls that we’ve all seen on lime leaves, even if we didn’t know what they were, but to identify the insect that caused them we need to know if we’re looking at a small-leaved lime, a broad-leaved lime or the very common hybrid between the two. Why is life never simple, I ask myself. Probably because it would be boring.
Having identified your species, it makes sense to take a good detailed note of where exactly on the plant you found the gall – leaf rib, body of the leaf, stem, bud?
Secondly, take a number of photos (if it’s a leaf, take both sides). If you can zoom in or magnify, that’s a good idea too. Many galls can be identified right down the species just through a good photo. If you want to become a serious galler (or Cecidologist) you might consider taking specimens and even rearing the inhabitants of the galls until they emerge, blinking, into the big wide world, but it’s not necessary for most people.
Thirdly, get yourself a good guide. If you are just beginning, Heal recommends this one:
But if you’re more serious, this is the one to go for, and apparently a new edition is due out soon.
And if you are really, really serious, the New Naturalist on plant galls has everything you ever wanted to know. This one is, I think, out of print, but you can get one-off reprints of New Naturalists if you go to their website, or second-hand bookshops will often have them. After all, plant galls are not the most apparently interesting of subjects, though after Heal’s talk I imagine there might be a run on the title.
Then, Heal moved on to talk about the different organisms that cause galls, and there are a fair few of them. After all, if you are a delicate little larva, how nice it must be to be surrounded by a robust protective covering while you munch away to your heart’s content, and many unrelated insect groups have taken this route.
First, we have the gall midges (Cedidomyiidae), members of the fly family (Diptera). These are tiny creatures, many of whom are less than a millimetre long. They have these remarkable antennae that look like strings of beads. Heal showed a number of photos of the midges causing the leaf to curl around: while we might see the caterpillars of species like the peacock butterfly making themselves a shelter by stitching the leaves of nettles together, with these midges the plant itself is persuaded to grow in an unnatural way. You can see a picture of ash mid-rib gall, caused by a gall midge, below.
Gall midge (Photo Three)
Ash Midrib gall (Photo Four)
Then there are the gall wasps (Cynipidae), who produce some of the most well-known and spectacular galls, such as the oak knopper gall in Photo Two, and the Robin’s pincushion on roses. Within that multicoloured mass of ‘hairs’ is a many-chambered gall, each containing a tiny wasp larvae. Heal points out that if you open up a gall caused by an insect, what pops out might not be the creature that made the gall but another species entirely that is either a parasite, a predator or some other kind of free-loader.
Oyster gall on oak leaf
Then there are the gall mites (Eriophyidae), which are Heal’s favourite group, partly because they are so understudied and so it’s likely that there are some undiscovered species lurking in our back yards. They are not typically ‘mite-y’ looking, but, as Heal put it, they look more like carrots, long and slim. The gall that you might have seen most often is the Nail gall on lime leaves, which is rather beautiful in my opinion. Some of the galls contain microscopic ‘hairs’ which can be diagnostic for species. Some gall mites are pests of food crops, but others, such as the bindweed gall mite, are used for biological control of noxious weeds.
Lime Nail Gall (Photo Six)
A cereal rust mite (Photo Seven)
So, these are the three main groups of insects who can create galls, but there are many others; sawflies on willow, aphids on elm and some species of moth. Then there are the fungi that can induce galls. Mistletoe technically is a gall-causer – the tree produces distortion and swelling at the point of infection, induced by the parasite. And then there are endless bacteria and viruses that can cause galls.
Galls on crack willow caused by a sawfly (Photo Eight)
So this was a most interesting talk by James Heal – he pitched it perfectly for beginners, I wouldn’t be the least bit surprised if a whole new bunch of gallers has been inspired by his presentation. I certainly learned a lot, and it’s left me with a whole lot of things to ponder. If you’d like to listen to the whole thing (which I would recommend) you can find the link here.
Photo One by Lairich Rig / Silk button spangle galls on oak